The invention relates to ink jet printing devices and more particularly to an ink cartridge for an ink jet printer having customer replaceable ink supply tanks and air ingestion control.
Ink jet printing devices may include one or more printheads which eject ink onto a print medium, such as paper, in controlled patterns of closely spaced dots or pixels. To form color images, a printhead may have segregated groupings of nozzles, one group for each color or multiple printheads may be used, with each printhead being supplied with ink of a different color from associated ink supply tanks. For carriage type multicolor printers, which reciprocate back and forth across a stationary print medium to print a swath of information, one or more printheads are sealingly attached to a cartridge containing several replaceable ink supply tanks, generally one tank for each color of ink. The cartridge is mounted on a movable carriage which is translated back and forth along guide rails. Each time the cartridge traverses across the print medium, a swath of information is printed while the print medium is held stationary and then is stepped a distance of the height of the printed swath, so that the next swath may be contiguously printed against the previously printed swath. This procedure is continued until an entire page is printed.
Ink from each of the ink supply tanks is drawn by capillary action through an outlet port in the respective tank and into a respective passageway in the floor of the cartridge fluidly connecting ink to the designated printhead . The passageway supplies ink to the printheads from the respective ink tank replenishing the ink after each ink droplet ejection from the printhead nozzles. In order to obtain a more effective withdrawal of ink from an ink tank, it is known to project an ink pipe into the ink container so as to withdraw either liquid ink or ink from an impregnated foam member. U.S. Pat. No. 4,771,295 is representative of this type of ink withdrawal system.
It is well known that customers or users of ink jet printers may have ink cartridges with permanently fixed printheads and replaceable ink supply tanks. For existing multicolor ink jet printers, it is not uncommon for the printer to deplete ink from many ink supply tanks of each color before having to replace the cartridge and its attached printhead. One problem with the replacement of depleted ink tanks, is that when the filters required to filter the ink are recessed in the ink pipes, an air pocket is formed in the ink pipe above the filter when the depleted tanks are removed. When the new tank is installed, the air over the filter is trapped in the ink pipe between the filter and the foam in the ink tank. As soon as the printhead is re-primed, as is necessary each time the ink tank is removed, the trapped air is drawn into the printhead's reservoir and/or capillary ink channels where it is trapped and causes an interruption of capillary flow, thus causing at least some of the nozzles to misfire, if not total deprime of the printhead.